Institut de Biologie du Développement de Marseille-Luminy, CNRS UMR 6216, case 907, Parc scientifique de Luminy, 13288 Marseille cedex 9, France.
Nature. 2011 May 5;473(7345):83-6. doi: 10.1038/nature09977.
Body plans, which characterize the anatomical organization of animal groups of high taxonomic rank, often evolve by the reduction or loss of appendages (limbs in vertebrates and legs and wings in insects, for example). In contrast, the addition of new features is extremely rare and is thought to be heavily constrained, although the nature of the constraints remains elusive. Here we show that the treehopper (Membracidae) 'helmet' is actually an appendage, a wing serial homologue on the first thoracic segment. This innovation in the insect body plan is an unprecedented situation in 250 Myr of insect evolution. We provide evidence suggesting that the helmet arose by escaping the ancestral repression of wing formation imparted by a member of the Hox gene family, which sculpts the number and pattern of appendages along the body axis. Moreover, we propose that the exceptional morphological diversification of the helmet was possible because, in contrast to the wings, it escaped the stringent functional requirements imposed by flight. This example illustrates how complex morphological structures can arise by the expression of ancestral developmental potentials and fuel the morphological diversification of an evolutionary lineage.
身体模式，它描述了具有高分类等级的动物群体的解剖组织，通常通过减少或失去附属物（例如脊椎动物的四肢和昆虫的腿和翅膀）来进化。相比之下，新特征的添加极其罕见，并且被认为受到严重限制，尽管限制的性质仍然难以捉摸。在这里，我们表明树蝉（膜翅目）的“头盔”实际上是一个附属物，是第一个胸节上的翅膀系列同源物。这种昆虫身体模式的创新在 2.5 亿年的昆虫进化中是前所未有的。我们提供的证据表明，头盔的出现是通过逃脱由 Hox 基因家族成员赋予的对翅膀形成的祖先抑制而产生的，该家族沿着身体轴塑造了附属物的数量和模式。此外，我们提出，头盔的异常形态多样化是可能的，因为与翅膀不同，它逃脱了飞行所施加的严格功能要求。这个例子说明了复杂的形态结构如何通过表达祖先的发育潜力而产生，并为进化谱系的形态多样化提供动力。
